Hi:

I am simulating flow of air in pipe (long pipe with lots of elbow, bends etc) by FLUENT. I am using standard k-e turbulent model with standard wall function. My questions are:

1. Should I check wall y+ or y* value?

2. Lets say the y+ value is in the limit 15-200. But according to the theory we know lower limit is 30. With this current simulation (i mean value 15) what kind of error (%) will be introduced to the pressure drop data? Will it be considerable or negligible?

3. Its a huge model (around 3 million cell) and I am afraid I cant refine the mesh anymore. What do you recommend from your experience?

Thank you guys. Munni

Hi!

1. YES! y+ is extreamly importand, if you want to report drag - wall sher stress is calculated using the wall low - and that dependes on the wall function!

2. I am not so sure about that...

3. Use boundary layer option. that will give you a small wall disdance, but enables one to have the next cell larger. That reduces the number of cells.

Ralf